Head for gas detectors



A ril 29, 1930.

J. K. MABBS HEAD FOR GAS DETECTORS Fild Aug. 13,

1928 2 Sheets-Sheet l (/fflNVENTORI ATTORNEYS,

April 1930 J. K. MABBS 1,7565794 HEAD FOR GAS DETECTORS Filed Aug. 15, 1928 2 Sheets=-Sheet 2 1N VENTOR:

A TTUR/VE V5.

Patented Apr. 29, 19 30 UNITED STATES some 1:. was, or;

PATENT- OFFlCE HEAD/FOB GAS nn'rncrons Application and August ,13, 1928. Serial No. 299,405.

My invention relates to gas detectors of the type in which a surface is heated in contact Wlth the atmosphere to be tested. If a combustible, as be resent in the atmosphere the gas will e oxi ized and additional heat generated, further raising the temperature of p the member the surface of which is heated. This increase in temperature may be measuredinany suitable manner but I prefer to w determine it bynoting the change in electrical resistance of the heated member, which is. preferabl a filament of chemically pure platinum. ile I have found a chemically pure platinum filament advantageous, especially when heated to a temperature in excess of l,000 C. my invention is not limited to s the use of any particular material or to any particular temperature.

An object of my invention is to provide a head or mounting for this filament in which the filament is surrounded by jackets of a material which resists the propagation of flame and which cannot be removed without breaking the circuit to the filament. Another as object of my invention is to provide a sim- Ipie inexpensive and reliable mounting for the ament inwhich. provision is made for preventing damage to the filament. These and other objects of my invention will be apparout from the following description having reference to the accompanying drawings in which;

Fi ure 1 is aside view, partly in section of a evice constructed in accordance with one embodiment of my invention;

Figure 2 is a vertical section through the filament holding unit;

Figure 3 is a top plan view of the filament holding unit; and

gure 4 is a horizontal section of the head taken on the line IV-IV of Figure 1.

The device is a modification of that disclosed in the copending application of W; F. Hunt, J. K. Mabb's, and W. B. Rowland, Se-

rial Number 229,406, filed August 13, 1928. In the device shown in the drawings a base '10 is mounted on a handle 11, this handle being provided with a suitable index so that the position of the device may be noted. A

59 cable 13 is led into the base in any suitable is mounted. The shell is made of conducting material and is provided with a-conductor 19 extending therefrom for purposes to be described below. A-spring 21 fits around the outside of the shell in the opening 17 engag ing a shoulder 22 provided therein and one end extends through the block and is connected to the conductor 19. The shell is provided with one or more slots 23 for receiving pins 24 on the filament holding unit. I prefer to employ two such slots and pins.

The filament holding unit consists of a. cup 25 upon which the pins 24 are mounted. A pair of standards 26 and 27 are secured within the cup, the standard 26 being electrically connected to the cup and the standard 27 being insulated therefrom and terminating in a contact member 28 below the bottom of the cup. Surrounding the cup is a carryingring 29. This ring is provided with screws 31 for engagement with a flame arresting jacket. The screws are rotatably secured in the carrying rings in any suitable manner so as by beading a portion of the screw over a shoulder in the hole through which the screw passes.

' In order to prevent the propagation of flame from the gas burning around the filament to the atmosphere being tested, I surround the filament with two or' more jackets of a suitable flame arresting material such as the wire gauze that is used in the well known miners flame safety lamp. These jackets are preferably cylindrical with a gauze top and are provided with flanged bases. The base of the inner jacket'is provided with threaded apertures to receive the screws 31. The carrying ring 29 engages the base 32 of the inner protective jacket 33 with a close fit whereby considerable timehis required to remove the carrying ring from the base. This is due to the arrangement of the screws in the carryng ring. As one screw is unscrewed the car- 109 rying ririglbindsagainst the base of the gauze screw. e opposlte screw must then be similarly unscrewed a short distance and each screw must then be alternately unscrewed a short distance. The base 32 of the inner jacket is provided with one or more holes,-preferably two, through which extend projections 34 on the base 35 of the next jacket 36.

The insulating block 14 is provided with holes opposite the projections 34 and in each of these holes is a plunger 37. These plungers are made in part at least of insulating material although they may be provided with conductive wear resistant material for enga ement with the projections 34. Dispose beneath the block are conductors 38, 39,

41 and 42. The conductors 39 and 41 are connected to conductors of the cable 13. The ends of'the conductors 38 and 39 and of the conductors 41 and 42 are in aligned spaced relation and the conductor 42 terminates-in a resilient portion 43 forming a contact for engagement with the contact 28 of the filament holding unit. The conductor 38 is connected to conductor 19. Thus when the plungers are forced downwardly a circuit is provided from the cable 13 through the conductors 39, 38 and 19 to the s ring 21 and thence to the pins 24 and to the. lament. The other side of the circuit is formed by the conductors 41 and 42, the contact 43 and the contact 28 on the base of the filament holding unit. Surrounding the flame arresting jacket 36 I may provide additional flame arresting jackets such as the jacket 44. This jacket is provided with a flanged base 45 resting upon the base 35. Suitable means are provided for holding the protective jackets in place around the filament such as that disclosed in the drawing which consists ofa lockin ring 46 which has an inwardly disposed ange for engaging the base of the outer jacket. The height of the locking ring is such that the plungers 37 will not be forced downwardly to close the circuit unless all the protective jackets are in place. I may if I so desire provide a protective bonnet 47 surroundingthe outer portion of the flame arresting jacket.

The standards 26 and 27 are held in spaced relation by a spacing member 51, which is composed at least in part of non-conducting material. The upper ends of the standards are formed into flat surfaces'upon which bearing members 52 rest. These bearing members are held to the top of the standards by any suitable means as by screws 53 and the ends of a filament 54 are gripped between the bearing members and the tops of the The bearing members are pro vided with prongs 55 extending upwardly and inwardly to serve as a protection for the filament.

I claim: 1. In a gas detector head the combination of a base, a plurality of gauze jackets above said base in coaxial relation, a filament within said jackets, means including a switch on said base for supplying current tosaid-filament and means carried by one of the outer jackets for operating the switch.

2. Ahead for gas detectors comprising a base member, a gauze jacket having a base engaging said base member, means for mountvided with an aperture and said switch operating means is a projection on the base of the second mentioned jacket extending through said aperture.

4. A head for gas detectors comprising, in combination, a base member, means engaging said base member for supporting a filament, means including a switch for supplying current to said filament, means for actuating said switch disposed below the up er face of said base member, a plurality o protective jackets enclosing said filament, and means carried by an outer jacket for operating said switch actuatin means.

5. A device as claime in claim 4in which the jackets are provided with flanged bases, the switch operating means is a rojection extending downwardly from one o the bases, and the bases of the jackets within the jacket carrying the operating means are rovide'd with apertures through which sai operating means may project. 7 Q

6. A head for gas detectors comprising-a block, a protective jacket having a flanged base engaging said block, said'base being provided with an aperture, a filament holding unit engaging said base and said block, conductors including a switch on said block for supplying current to the filament, switch actuating means disposed below the upper surface of saidblock, outer jackets surrounding said first mentioned jacket, said outer jackets having flanged bases and means on the base of one ofsaid outerj ackets adapted to extend through the aperture in the base of the inner jacket and operate the switch actuating means.

1 7. A filamentholding unit comprising a tion of a filament holding unit and a proteetive gauze jacket provided with a base, and screws rotatably mounted and axially fixed on said unit for holding said unit in engagement with, said base.

In testimony whereof, I aflix my signature.

JOHN K. MABBS. 

